1. Field of the Invention
The present invention generally relates to a disk apparatus, and more particularly to a head loading mechanism of a disk apparatus by which a head is placed in a loaded position on a magneto-optical disk when information is recorded on or reproduced from the disk by using the head, and the head is placed in an unloaded position that is separate from the disk before the disk is inserted into or ejected from the disk apparatus.
2. Description of the Prior Art
In a magneto-optical recording method, data is represented as the direction or intensity of magnetization of a disk material. A laser light beam is irradiated to one surface of a disk of magnetic material and the other surface of the disk is magnetized. The direction or intensity of magnetization of the disk material is varied by using a head in accordance with a data signal, so that information indicated by the data signal is recorded on the disk.
Two kinds of magneto-optical recording methods are known: one is the optical modulation recording and the other is the electromagnetic modulation recording. The optical modulation recording method is the earlier one of the two methods, and this method is applied to a magneto-optical disk apparatus for a practical use. In the optical modulation recording method, the intensity of laser light is modulated according to the data signal, and a recording medium is exposed to the modulated laser light so that the information is recorded on the recording medium.
However, it is difficult to overwrite data to the recording medium by using the optical modulation recording method. In overwriting, the recorded data on a disk is erased and new data is written to the disk.
On the other hand, the overwriting can be easily carried out using the electromagnetic modulation recording method. It is expected that the electromagnetic modulation recording method will be more widely spread. In the electromagnetic modulation recording method, the direction of magnetization of the recording medium is varied by a magnetic head in accordance with the data signal so that the information is recorded on the disk by using the magnetic head and an optical head.
In order to carry out the electromagnetic modulation recording method, it is necessary for the magnetic head to produce a relatively high magnetic field (in the order of 200 to 300 Oe) in the magnetic film of the recording medium. In order to increase the recording density of the disk, it is necessary to change the direction of magnetization of the disk material at higher rates. In order for realizing such improvements relating to the electromagnetic modulation recording method, several head loading mechanisms for magneto-optical disk apparatus have been proposed.
In a magneto-optical disk apparatus of the type in which the recording medium can be exchanged, a head loading mechanism is used for placing a head in a loaded position on a disk and for placing the head in an unloaded position that is separate from the disk. Before the disk is positioned to a read/write position in the apparatus or before the disk is ejected from the apparatus, the head is unloaded from the disk by the head loading mechanism. After the disk is placed in the read/write position of the apparatus, the head is loaded onto the disk by the head loading mechanism so that information is recorded on or reproduced from the disk by means of the head.
Japanese Laid-Open Patent Publication Nos. 3-19159 and 3-19160 disclose a head loading mechanism for a magneto-optical recording device of the type in which a disk as the recording medium is changeable. In this head loading mechanism, an elastic member for supporting a magnetic head is repeatedly subjected to elastic deformation when the recording medium is changed.
In the head loading mechanism disclosed in the above mentioned publications, the loaded position of the magnetic head relative to the disk may significantly vary if the disk is changed many times to subject the elastic member to the repeated deformation. Variations in the loaded position of the magnetic head relative to the disk may cause problems with the data recording or may damage the head by the interference between the head and the disk cassette. Thus, this head loading mechanism has a problem in that the reliability of the magneto-optical recording is somewhat lowered because of the use of the elastic member.
Japanese Laid-Open Patent Publication No. 3-104068 discloses a head loading mechanism for a magneto-optical disk apparatus. In this head loading mechanism disclosed in this publication, the magnetic head is supported by a thin leaf spring when the head is in its unloaded condition for the changing of a disk. The leaf spring is supported by upper and lower plates and other parts when the head is in its loaded condition, so that the magnetic head is supported by the leaf spring and the additional parts. The rigidity of the head loading mechanism for supporting the magnetic head is thus increased with the additional parts.
However, the weight of the head loading mechanism disclosed in the above mentioned publication is raised by the additional parts, which will make the goal of high disk access speed more difficult to achieve. Also, the head loading mechanism disclosed in this publication requires many additional parts and the structure is complicated. Thus, the manufacturing cost will become high.